DescriptionIn adults, the head is much broader than long, is very depressed, scarcely projecting; no canthus, loreal oblique, slightly concave; internarial distance greater than interorbital space, which is less than the width of the upper eyelid; tympanum not very distinct, about half the diameter of the eye; tibiotarsal articulation reaches the temple or posterior border of the eye; digits obtuse or slightly swollen at tips, toes entirely webbed, subarticular tubercles small; skin on body very loose; when the frog is on land, it is thrown in folds. Dorsum is smooth or tuberculated, tubercles are tipped with dark spines; sexually dimorphic: flanks of body of male are heavily tuberculated. Dark nuptial spines are present on the first two fingers and the inner carpal tubercle of males. There is a large patch of pustules on both ventral sides of the chest. Venter in male is tuberculate all over, while that of the female is smooth. The anterior limbs of the breeding male are considerably thickened (Khan 1986).

Coloration: Adults are olive brown or dark green above, with small irregular yellow, orange, or reddish spots; ventrum white with profuse fine dark brown or black mottling. Juveniles dark brown or olive, with blackish blotches. Pupil reduced to a narrow slit. A transverse dark streak runs across the eye, a similar vertical streak runs downward across the goldenbrown iris, giving the eye a peculiar appearance. This feature is also present in tadpoles (Khan 1986).

The body of the tadpole is elongated, bulging, eyes are anterodorsal, tail very muscular, with broad dorsal and narrower ventral fins, acutely pointed tip.
The anteroventral oral disc is surprisingly small for this heavy and broad-bodied large tadpole. Fringe of oral papillae does not extend along anterior labium, however it is entire along posterior labium. Beak narrow, finely serrated, labial tooth row formula is 5(4)/3.
Total length of the tadpole 78-80 mm, tail 50-52 mm (Khan 1986).

Found in Pakistan (Baluchistan and Kashmir), India (Kashmir), Afghanistan. The karez frog abounds around Quetta and Mastung in karez channels (Khan 1987; Khan and Ahmed 1987). It has also been reported from Afghanistan up to 1800-2000 m in elevation (Kullmann 1974).

Life History, Abundance, Activity, and Special BehaviorsChrysopaa sternosignata is a thoroughly aquatic species, inhabiting clear pools with flowing karez water. When disturbed it jumps into the depths of the water and hides under gravel at the bottom or under dense marginal vegetation and thick floating algal cover. The frog never leaves the water; even in freezing winter when the upper water surface is frozen, it remains sluggishly active beneath in the unfrozen water. In summer it usually sits in the marginal vegetation or under undercut rocks along sides of streams (Khan and Ahmed 1987).

Reproductive activity is at its peak from April to June. Males call from the margin of flowing water at sunset. The call is a low-pitched melodious "Taroon, taroon, taroon" uttered three to four times rapidly. One has to wait for 5-10 minutes to hear the next outburst of calls. Calling males are solitary. Eggs are large (2.6-3.0 mm) and laid in groups enclosed in jelly coats, which soon are attached to the submerged vegetation. Abortive interspecific amplectic pairing is common between
Chrysopaa sternosignata and Euphlyctis cyanophlyctis (Khan and Ahmed 1987).

The tadpole is the largest and stoutest of all Pakistani tadpoles. It coexists with tadpoles of Euphlyctis cyanophlyctis and Bufo viridis in karez water, later mostly confined to side pools. The tadpole feeds on algal vegetation amply available in the karez channel (Khan 1986).

The frog feeds on insects, crabs, small fishes, dragonflies, and a host of other water-visiting arthropods (Khan 1986).